Process for manufacturing white-lead color.



UNITED STATES PATENT orrioE.

ADOLF WULTZE, OF OHARLOTTENBURG, NEAR BERLIN, GERMANY.

PROCESS FOR MANUFACTURING WHITE-LEAD COLOR.

Specification of Letters Patent.

Patented Oct. 10, 1905.

Application filed October 31, 1904:. Serial No. 230,769.

- specification.

My invention relates to a process for manufacturing white-lead color, and more especially a kind of precipitated white lead, as precipitated out of solution of lead salts. For this purpose basic solutions of lead have been hitherto used as starting materialas, for instance, obtained by dissolving litharge in neutral acetate of lead. It is also known that carbonate of lead can be precipitated by introducing for a longer time carbonic acid into neutral acetate of lead, (solution of sugar of lead.) The product obtained thereby is, however, crystalline and does not possess any covering power at all. Now I have found out that an excellently covering white color can be obtained by introducing carbonic acid into neutral sugar of lead, thereby obtaining a product far superior with regard to quality and covering power to the white lead hitherto known. Thenewfeatureofmyprocessconsists therein that the carbonic acid is introduced into the neutral solution of sugar of lead under pressure. A diluting of the solutions increases in this process the yield. The composition of the new lead color is about that of the normal carbonate of lead. The ordinary white lead, which is regarded to be two-thirds carbonate of lead, contains theoretically 11.36 per cent. of carbonic acid, and the normal carbonate of lead contains, according to the theory, 16.49 per cent. of carbonic acid. The new precipitated white lead according to my invention, however, has an average of about 16.05 per cent. of carbonic acid.

A solution of sugar of lead containing ten to fifteen per cent. of acetate of lead is used, and the precipitation takes place the best at an air temperature of 10 to 20 Celsius.

During the process a small increasing of the temperature results at the introduction of carbonic acid, the pressure, being about one atmosphere, shall be very suddenly produced in the precipitating-receptacle. The end reaction can be seen from the fact that scum flows out of the safety-valve of the precipitating-receptaclethat is to say, that a further precipitation of carbonate of lead does not take place. lVhen a solution of acetate of lead having ten per cent. of acetate of lead is used, seven per cent. of carbonate of lead is precipitated, while the rest of three per cent. is used again afterward. When more than fifteen per cent. of acetate of lead is contained in a solution, the carbonate of lead is considerably heavier, and when the concentration is further increased the carbonate of lead becomes crystalline. With respect to the construction of the precipitating-receptacle, it can be provided with a stirring work or not.

Having thus fully described the nature of my invention, what I desire to secure by Letters Patent of the United States is Process for manufacturing white-lead color, consisting in treating aqueous solutions of neutral acetate of lead With carbonic acid under pressure.

In witness whereof I have hereunto set my hand in the presence of two witnesses.

ADOLF WULTZE.

Witnesses:

HENRY HAsPER, WOLDEMAR HAUPT. 7 

